1. Field of the Invention
The present invention relates to semiconductor or flat panel substrate processing systems. More particularly, the present invention relates to techniques and apparatus for automatically determining the substrates states in semiconductor processing chambers.
2. Description of the Related Art
Within the semiconductor industry, an ever present need exists for improved process repeatability and control. As new generations of integrated circuits employ smaller feature sizes than were contemplated in previous generations, greater demands are placed on the integrated circuit fabrication process. Deposition and etching one or more layers of a semiconductor substrate in a plasma environment are two of the most common steps in integrated circuit manufacturing. To ensure that a correct quantity and quality of film is deposited or etched, the plasma state of the process chamber needs to be monitored comprehensively prior to, during and after production substrate processing.
During a plasma process, certain plasma “attributes”, such as the plasma's optical electromagnetic emissions, the RF power delivered to a wafer pedestal, wafer reflectance (WR) (or substrate reflectance), process pressure and process temperature, manifest low frequency fluctuations that contain significant information about the plasma process and the plasma chamber. The intensity of a plasma's optical electromagnetic emission (OES), the fluctuations of the RF power delivered to a wafer pedestal, and the substrate reflectance (SR) during plasma processing contain information related to process state, process event and process chamber. OES, RF, and substrate reflectance states are affected to different degrees by varying chamber conditions and by process parameter changes. OES, RF, and substrate reflectance data are complementary to one another. Inclusion of these data during process or chamber monitoring is more comprehensive than merely including one of the three types of data. Details of how a chamber and process can be monitored during process to detect endpoint and fault have been disclosed in commonly assigned U.S. Pat. No. 6,368,975, entitled “Method and Apparatus For Monitoring A Process By Employing Principle component Analysis”, issued on Apr. 9, 2002, its divisional application Ser. No. 10/341,696, filed on Jan. 14, 2003, and U.S. patent application Ser. No. 10/628,001, entitled “Method For Automatic Determination of Semiconductor Plasma Chamber Matching and Source of Fault by Comprehensive Plasma Monitoring,” filed on Jul. 25, 2003, each of these patent and patent applications are incorporated by reference herein in their entireties.
At various stages of semiconductor or flat panel display substrate processing, substrates have different layers of materials on top. These different layers of materials have different thickness in each layer, which could be patterned to have different pattern densities and different critical dimensions (CDs). Some layers on the substrate could be doped with different dopants. The various materials on the substrates contribute to the state of the substrate (or substrate state). At various steps of substrate processing, incorrect processing or mis-processing could occur which could make the substrate fall out of the control limit. A substrate could receive too much deposition, which results in a film being too thick, or the deposition condition is not optimal, which results in a film with poor quality. Photolithography processing could have drifted to result in poor critical dimensions (CDs) on the substrate, i.e., the CDs are too small or too large. Poor etching processing could also affect critical dimensions (CDs). For the advanced processing in modern IC manufacturing, detecting substrates with previous processing steps out of specification is very important, since process drift could be interrupted to cause further mis-processing and also substrates that have already been mis-processing could either be reworked or be scratched to prevent further loss of manufacturing resources.
Therefore, there is a need in the art for techniques for automatically determining the state of a substrate in a processing chamber to determine if the substrate suffers mis-processing prior to or during processing in the process chamber.